Electric power companies and utilities generate electrical power for consumers using power generation units. A power generation unit can be a coal-fired power plant, a hydro-electric power plant, a gas-turbine-driven generator, a diesel-engine-driven generator, a nuclear power plant, etc. The electrical power is transmitted to the consumer via transmission and distribution (T&D) systems. T&D systems can include power lines, protective switches, sectionalizing switches, breakers, reclosers, etc.
Electrical power is typically transmitted over a portion of the T&D system at relatively high voltages to minimize losses. T&D systems typically include transformers that step up the voltage to levels suitable for transmission with minimal losses. Transformers are also used to step down the relatively high transmission voltages to levels suitable for use by the consumer.
The malfunction or failure of a transformer can result in a power outage. The malfunction or failure of a relatively large transformer used, for example, in a substation can result in a power outage that affects a large numbers of consumers. Hence, purchasers of transformers (typically electric power companies and utilities) usually consider transformer reliability when making their buying decisions.
In addition, transformer purchasers usually consider the initial (purchase) cost and operating costs when deciding whether to purchase a particular transformer. The cost of the materials used in the manufacture of a transformer, in general, represents a substantial portion of the purchase cost.
Operating costs are due in large measure to the internal losses within the transformer. These losses, in turn, are related to the efficiency of the transformer. Hence, purchasers of transformers usually demand that transformer manufacturers provide a product with a relatively high efficiency. Purchasers sometimes negotiate a contractual financial penalty from the manufacturer if a transformer does not meet a specified efficiency goal.
In view of the above demands, transformer manufacturers generally attempt to design their products so as to maximize the reliability and efficiency thereof, and to minimize the initial (purchase) cost.
Transformers typically undergo acceptance testing before being shipped to the customer or end user. Acceptance testing is used to verify that the transformer meets certain limits, guarantees, goals, or other requirements, e.g., internal losses below a predefined value (these limits, guarantees, goals, and requirements are hereinafter referred to collectively as “performance requirements.”)
A transformer that exceeds its performance requirements may be over-designed, i.e., one or more components of the transformer may be constructed to perform at a level beyond that which is necessary. For example, a transformer that exceeds its requirements for internal losses, i.e., a transformer having lower internal losses than required, may use more steel in its core than necessary.
A component that over-performs is likely more expensive than necessary. Hence, over-performing components can potentially result in lost profits for the manufacturer. Over-performing components can also represent a lost opportunity to lower the price of the transformer and thereby make the transformer more cost-competitive.
A transformer that fails to meets its performance requirements, conversely, may have one or more under-designed components. Modification of such components is usually required for the transformer to meet its performance requirements (and thereby avoid the financial penalties sometimes imposed on manufacturers for performance shortfalls). The required modifications may be relatively minor in some cases, and the benefits associated with such modifications may justify the relatively low expense associated therewith. In cases where major modifications are required, however, the benefits of such modifications may be outweighed by the expense thereof.